Field of the Invention
The present invention relates to an object information acquiring apparatus.
Description of the Related Art
There is technology called photoacoustic tomography (PAT) which involves irradiating an object section with pulsed light generated by a light source and, using a photoacoustic effect in which an acoustic wave is generated by absorption of light inside the object section, imaging internal tissue that acts as a generation source of an acoustic wave. Proposals are being made to utilize this technology for imaging of physiological information (in other words, functional information) of a living organism.
Generally, an electrical signal acquired from an acoustic wave detecting element in photoacoustic tomography contains, in addition to a signal attributable to an acoustic wave generated from inside a living organism, electrical noise propagated by capacity coupling with a metallic member of a case, a ground line, or the like. Examples of electrical noise include switching noise of a direct-current switching power supply. In addition, when an apparatus is provided with a stepping motor or the like, a large amount of electrical noise tends to be generated by the motor and peripheral circuits thereof when a drive coil is energized by an input of a control signal or by switching. In order to obtain a diagnostic image with good quality, the effect of such electrical noise on the image must be reduced.
With respect to this problem, Japanese Patent Application Laid-open No. 2011-200381 describes a noise reduction method in a system including a plurality of motors, peripheral circuits thereof, and an acoustic wave detecting element. FIGS. 9A and 9B are diagrams showing examples of an electrical signal output from a probe, in which FIG. 9A represents a state during operation of a motor and FIG. 9B represents a state during stoppage of the motor. In Japanese Patent Application Laid-open No. 2011-200381, at least a part of the operation of the motor is stopped during a period where the acoustic wave detecting element receives an acoustic wave. Accordingly, a signal of the acoustic wave detecting element makes a transition from a state where the signal includes electrical noise of the motors and peripheral circuits thereof as shown in FIG. 9A to a state where the signal does not include electrical noise of the motors and peripheral circuits thereof as shown in FIG. 9B.
Patent Literature 1: Japanese Patent Application Laid-open No. 2011-200381